import UIKit
@available(iOSApplicationExtension, unavailable)
@objc open class IQTextView: UITextView {
    @objc required public init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        NotificationCenter.default.addObserver(self, selector: #selector(self.refreshPlaceholder), name: UITextView.textDidChangeNotification, object: self)
    }
    @objc override public init(frame: CGRect, textContainer: NSTextContainer?) {
        super.init(frame: frame, textContainer: textContainer)
        NotificationCenter.default.addObserver(self, selector: #selector(self.refreshPlaceholder), name: UITextView.textDidChangeNotification, object: self)
    }
    @objc override open func awakeFromNib() {
        super.awakeFromNib()
        NotificationCenter.default.addObserver(self, selector: #selector(self.refreshPlaceholder), name: UITextView.textDidChangeNotification, object: self)
    }
    private var placeholderInsets: UIEdgeInsets {
        return UIEdgeInsets(top: self.textContainerInset.top, left: self.textContainerInset.left + self.textContainer.lineFragmentPadding, bottom: self.textContainerInset.bottom, right: self.textContainerInset.right + self.textContainer.lineFragmentPadding)
    }
    private var placeholderExpectedFrame: CGRect {
        let placeholderInsets = self.placeholderInsets
        let maxWidth = self.frame.width-placeholderInsets.left-placeholderInsets.right
        let expectedSize = placeholderLabel.sizeThatFits(CGSize(width: maxWidth, height: self.frame.height-placeholderInsets.top-placeholderInsets.bottom))
        return CGRect(x: placeholderInsets.left, y: placeholderInsets.top, width: maxWidth, height: expectedSize.height)
    }
    lazy var placeholderLabel: UILabel = {
        let label = UILabel()
        label.autoresizingMask = [.flexibleWidth, .flexibleHeight]
        label.lineBreakMode = .byWordWrapping
        label.numberOfLines = 0
        label.font = self.font
        label.textAlignment = self.textAlignment
        label.backgroundColor = UIColor.clear
        label.isAccessibilityElement = false
        #if swift(>=5.1)
        label.textColor = UIColor.systemGray
        #else
        label.textColor = UIColor.lightText
        #endif
        label.alpha = 0
        self.addSubview(label)
        return label
    }()
    @IBInspectable open var placeholderTextColor: UIColor? {
        get {
            return placeholderLabel.textColor
        }
        set {
            placeholderLabel.textColor = newValue
        }
    }
    @IBInspectable open var placeholder: String? {
        get {
            return placeholderLabel.text
        }
        set {
            placeholderLabel.text = newValue
            refreshPlaceholder()
        }
    }
    open var attributedPlaceholder: NSAttributedString? {
        get {
            return placeholderLabel.attributedText
        }
        set {
            placeholderLabel.attributedText = newValue
            refreshPlaceholder()
        }
    }
    @objc override open func layoutSubviews() {
        super.layoutSubviews()
        placeholderLabel.frame = placeholderExpectedFrame
    }
    @objc internal func refreshPlaceholder() {
        let text: String = text ?? attributedText?.string ?? ""
        if text.isEmpty {
            placeholderLabel.alpha = 1
        } else {
            placeholderLabel.alpha = 0
        }
    }
    @objc override open var text: String! {
        didSet {
            refreshPlaceholder()
        }
    }
    open override var attributedText: NSAttributedString! {
        didSet {
            refreshPlaceholder()
        }
    }
    @objc override open var font: UIFont? {
        didSet {
            if let unwrappedFont = font {
                placeholderLabel.font = unwrappedFont
            } else {
                placeholderLabel.font = UIFont.systemFont(ofSize: 12)
            }
        }
    }
    @objc override open var textAlignment: NSTextAlignment {
        didSet {
            placeholderLabel.textAlignment = textAlignment
        }
    }
    @objc override weak open var delegate: UITextViewDelegate? {
        get {
            refreshPlaceholder()
            return super.delegate
        }
        set {
            super.delegate = newValue
        }
    }
    @objc override open var intrinsicContentSize: CGSize {
        guard !hasText else {
            return super.intrinsicContentSize
        }
        var newSize = super.intrinsicContentSize
        let placeholderInsets = self.placeholderInsets
        newSize.height = placeholderExpectedFrame.height + placeholderInsets.top + placeholderInsets.bottom
        return newSize
    }
}
